Tip & How-To about Miscellaneous

Electrolytic capacitors in circuit board testing procedure with POWER OFF.

Electrolytic capacitors are most common and widely used in every electronic and electrical circuit boards ,they function good and smooth in circuit if they are in normal functioning order and if they are not healthier then they impact very bad on the whole electronic or electrical system,they can disable the whole circuit on and off ,erratic on and off, lower or block the system voltage ,lower or block the system current ,lower or block the system signals and also erratic system functioning.
now there is good procedure to grab any suspicious electrolytic capacitors to test them in the circuit board as well out from the circuit board with help of oscilloscope and 1000 cycle square wave 0.5 volt frequency generator, the generator for the electrolytic capacitor must not be above 0.5 volts range otherwise above this voltage range it will triggers the nearby transistor and ICs that will intrupt the test.
CAUTION. these all test are POWER OFF test,and capacitors should be all in fully discharged state, unplug the power from the system for these tests.
1) connect or touch the two leads of your square wave generator to the capacitors both leads it does not matter if it is positive or negative touch your oscilloscope lead and observe the signal , there is now no square wave signal passing instead you will observe a good triangle signal passing through oscilloscope screen it means it is a sign of healthy good capacitor,
compare it with the good one capacitor for double check.
2) connect or touch the two leads of your square wave generator to capacitors both leads it does not matter if it is positive or negative touch your oscilloscope lead and observe the signal , there is now square wave signal passing ,that is now become short in amplitude square wave signal passing through oscilloscope screen it means that capacitors become resistive or dried up or changed in value bad capacitor,electrolytic chemical inside is dried up,need replacement with the good identical one, compare with the another good capacitor for double check.
3)connect or touch the two leads of your square wave generator to capacitors both leads it does not matter if it is positive or negative touch your oscilloscope lead and observe the signal , there is now no square wave signal instead you will observe a bent or distorted square wave passing through oscilloscope screen it means it is a sign of bad capacitor, that have changed its value ,need replacement with identical one capacitor.
compare it with the good one capacitor for double check.
4) connect or touch the two leads of
your square wave generator to the capacitors both leads it does not matter if it is positive or negative ,then touch your oscilloscope lead and observe the signal , there is square wave signal with no change in amplitude you will observe a signal passing through oscilloscope screen it means it is bad complete dried up capacitor showing very high resistance in the circuit board ,need replacement with good identical one capacitor.
compare it with the good one for double check.



















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fail capacitors how to replace


Hello,

If capacitors are electrolytic types, then they have polarity + and -, and always are a mark on the pc board and it could be marked with either the "+" symbol or "-" capacitor has a mark itself that denotes polarity also, the most common mark i have seen is "-" running from top all the way down at a side of cap, you just have to buy them same voltage and capacitance rating and install them verifying TWICE the correct polarity and you are done, Mouser electronics has a wide stock of electrolytics, but remember polarity otherwise you will get a very big pop.

Oct 27, 2013 | Behringer BXR1800H Ultra Compact 180 Watt...

1 Answer

Most of the time, when the receiver is powered up, and after a few seconds, there will be a loud hum and POP from the speakers, the PROTECTOR display will flash. This does not happen every time the unit is powered up, but more than half of the time. If I shut down the unit , wait a couple of minutes...the receiver may power up OK , or may pop and go into PROTECTOR mode again. So far, no fuses have blown. In order to avoid the problem, I've resorted to keeping the receiver powered up 24/7. Until recently, this receiver has performed flawlessly since purchased in 1999, and I really like it, so, would like to keep it operational. I am a ham radio operator and hold a commercial radiotelephone license, I have no problem doing the repair, but, help with diagnosis will be appreciated. Ted Brough


Hi Ted,

First of all, thank you for posting your question here at Fixya.com.

"Protector/Protect" is an error code for out-of-regulation condition either on the power supply board and/or on the Sound output circuitry.
I've encountered this kind of symptoms not only on Sony home audio sound system but in almost known brands and the faulty parts are the same >>>> smoothing/filter electrolytic capacitor.
This is very common most especially on older unit because the capacitor begin to dried up resulting to voltage/audio out-of-regulation. In the first stage of fault, warm up will make itself stable but it will get worst as times goes by.
This is fixable and not a costly repair because this is one of the cheapest part on the board and widely available at electronics supply and online. You must have a test instrument (capacitor checker/tester) because not all capacitor that are look physically fine is in good condition, capacitor checker will reveal its condition.
Watch the video below for more info regarding electrolytic capacitor.




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For efficient troubleshooting, you must know which section/board are going to repair. In your case, AC board, DC board, REAR-AMP board, and the mainboard(Sound output circuitry) are going to troubleshoot.




12_10_2011_5_25_50_am.jpg

> Check or replaced C905 on AC board - this board is where the AC power cord's directly connected.
> Check or replaced C801, C803, C804, C807, C808, C809 on DC board - this board is where the two larges electrolytic capacitor is located.
> Check all electrolytic capacitor on REAR AMP board most especially in front of IC701(UPC2581V)
> Check the electrolytic capacitor in front and at the back of IC501 and IC601 (both UPC2581V) on the mainboard.

Note : IC501, IC601, IC701 are mounted on aluminum heat sink. Concentrate first on AC and DC board.

Once you've isolated the faulty electrolytic capacitor, your unit will back to normal again.

Hope I helped you.
Rating and feedback are highly appreciated.
Have a nice day! Good luck and take care!

Kind Regards,
Jdvillanueva

Dec 10, 2011 | Sony STR-DE835 Receiver

1 Answer

WhenI turn the TV on it clicks on & off many times before it accutually turns on ! It's like a switch is going bad1


The switch is ok it's the power supply board.
If this set is under warranty you should return it to get it repaired/replaced by the seller. If not then;
This sounds like the power supply board is failing. The electrolytic capacitors on the board may need to be replaced.

IF YOU KNOW HOW TO WORK WITH ELECTRONICS REPAIR(soldering ) or have a friend with knowledge/skill you can fix it.

>Unplug the set and any cables.
> lay the unit face down on a smooth flat surface. Make sure no pressure is against the LCD screen since it will crack easily. Support it by the edges.

>Remove the back cover.

>look at the capacitors on the power supply board. If the top of any of them are bulging up then that is the problem.

>You will have to replace ALL the electrolytic capacitors except for perhaps the 2 large ones.
>Disconnect and remove the power supply board. Handle by the edges to prevent contaminates and static electricity.
> Use ones with the Low Equivalent Series Resistance ESR rating
> Use ones with the same farad rating

> Use ones with the same or higher voltage rating
> Use ones with high temperature rating
> Install one at a time to prevent mix-up and keep the polarity correct.

> Leave a space between the PC board and the bottom of the capacitors for expansion. They heat up.
> Replace power supply board and reconnect cables..
> Replace back cover.


THIS IS AN INDUSTRY WIDE PROBLEM AFFECTING MANY COMPANIES AND PRODUCTS.

Sources for some good capacitors are www.digikey.com or NTE. Try nteinc.com for a local outlet of NTE products.
You can also search for other sources. Some companies even sell all the capacitors in a kit.


Total price of parts should be < $30.00

Yes you can buy a new power board but if the capacitors have not been replaced they will eventually fail also.

The board will look something like;

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Mar 05, 2011 | Samsung LN-T5271F 52 in. LCD Television

3 Answers

proton radio


I simply cleaned my red switch by spraying it with tuner cleaner and the problem went away (it will return in a few years and cleaning it will correct it again). The switch can only be cleaned with the radio open. A can of tuner clean/lub with a small straw will be needed.

Sep 24, 2008 | Proton R5A Clock Radio

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